The best way to not feel hopeless is to get up and do something. Don’t wait for good things to happen to you. If you go out and make some good things happen, you will fill the world with hope, you will fill yourself with hope.
The hole in one's heart gets filled by others around you. Friends won't flock to someone who abandons the memory of his friends and gives up on the world just because things don't go the way he wants them to. That won't help fill the hole in your heart. And people won't help those who run away and do nothing. As long as you don't give up, there will always be salvation.
Do not count the days, do not count the miles. Count only the Germans you have killed. Kill the German - this is your old mother's prayer. Kill the German - this is what your children beseech you to do. Kill the German - this is the cry of your Russian earth. Do not waver. Do not let up. Kill.